Ventajas
If you are lucky to work in a group with a good manager, working at NI can be wonderful. A good manager being defined as someone who understands work/life balance and is flexible with your work schedule where possible, someone who advocates for you, etc.
Desventajas
NI needs to fix issues with salary compensation. The average salary increase this year, after talking to some co-workers, seemed to be around 2-3%. If you were one of the lucky few to get an increase in the spring and fall, you probably got a total of 4-5% across the two adjustments. However, if you look at the last proxy statement (public on ni.com), the senior officers of NI saw an increase in salary and bonus compensation (not including stock) of between 31% and 50% from 2009 to 2010. That's just ridiculous. And lest you think the difference is that the average employee salary increases quoted above don't include bonuses - the average employee isn't receiving an extra 50% of their salary in a bonus - not by a long shot - but the senior officers are.